Automatically compensating cable connection



March 1s, 1947. J, L, ALDRED, JR 42,417,581

AUTOMA'IICLLYv COMPENSATING CABLE CONNECTION Filed DSG. 31, 1942 PatenteduMar. 18, 1947 AUTOMATICALLY COMPENSATING CABLE CONNECTION John L. Aldred, Jr., Fort Worth, Tex., assignonby mesne assignments, to Consolidated Vultee Aircraft Corporation, a corporation of Delaware Application December s1, 1942, serial Ne. 470,885

1 Claim. (01.267-1) The invention relates to cable-connections used for controlling or shifting rudders, ailerons, elevators, aps, and other devices. These connections usually extend between a control element within reach of the pilot and a remotely located control surface which is to be operated. These cable connections are adapted to perform their work by a pull on the cable and are usually of considerable length because they extend between the pilots cabin and the controlled device which is remotely located fromthe ca'bin.

Airplanes operated in a wide range of altitudes are subjected to extremes of atmospheric temperature. For example, an airplane at ground level' where the atmospheric temperature is approximately 100 F. may ascend for travel to an altitude of 30,000 feet where the temperature will normally be approximately -48f7 F. These changes in temperature cause expansion and contractionof the aircraft structure on which the elements and cable-connections are mounted, particularly in large airplanes constructed of aluminum alloy. Cables used for operating the control surfaces are made of steel which does not have the same coecient of expansion as the aluminum alloy used in the structure on which the cable and elements connectedthereby are mounted. In some instances the cables extend through heated areas inside of the aircraft body and are exposed to the outside air for only a portion of their length, whereas the outer surface of the airplane body is exposed for its yentire length. These cable-connections are normally stressed to a predetermined tension when the n airplaneI is located where the temperature is moderate. If the cable is under predetermined or correct tension while the aircraft is on the ground or where the outside temperature, is modcrate and the airplane travels to high altitudes, the contraction of the airplane structure resulting from the low temperature will produce slack in the cable. Such slack will render the operation of the controlled elements inaccurate or unsatisfactory or may render them inoperative. A desideratum in aircraft is to maintain the cable connections under a predetermined tension at alltimes.

The primary object of the present invention is to provide a tension regulating device for automatically maintaining the night control cables of an airplane at a substantially uniform and predetermined tension so that the controls will remain effective and satisfactory notwithstanding extreme variations in the atmospheric temperature which cause contraction of the airplane structure. v

Another object of the invention is to provide a simple and efficient device which forms a link in a cable-connection for shifting or controlling elements on aircraft and by which the desired predetermined tension will be maintainedffor correct operationl at the extreme atmospheric temperatures in which the airplane is operated.

Other objects of the invention will-appear from the detailed description.

The invention consists in the several novel features which are hereinafter set'forth and more particularly defined by claimA at the conclusion hereof. i l

In the drawings:

Fig. l is a longitudinal section of a cable connection embodying the invention,

Fig. 2 is a .detail section of a modied form o'f device for controlling the passage of the hydraulic fluid through the piston.

'I'he invention is exemplied in connection with a cable comprising sections a and a1, and an automatic tensioning device between and connecting said cable-sections. One of the cablesections may be connected to a, shiftingelement such as a lever or other device whereby a pull may be exerted on the cable, and the other is connected to an element which is controlled or operable by a, pull exerted upon the other cable. section. The cable-sections and the connectingdevice form a connection which is designed to be normally maintained under sufficient tension to avoid slack which must be taken up when the connection is pulled in one direction by the control element in the cab. The connecting device between the cable-sections automatically regulates the tension to maintain the cable taut.

This automatic device. comprises a casing III which is provided adjacent one of its ends with a cylinder II. The casing I0 at said endhas screw threaded thereto a head I2 which has an eye I3 integrally formed therewith.l Cable section a1 has one of its ends provided with a suitable fitting or yoke I4 which is coupled to the eye I3 by a pin or bolt I5. A piston I6 is slidably mounted4 in the cylinder II and has a peripheral packing ring 30 for preventing the hydraulic iluid from leaking around the piston. A piston-stem I1 is provided with a head I8 which abuts against the outer face of piston I6. Stem I1 extends, and is slidable, through one end of the casing I Il and a packing I9 is held by a cap and gland I9 in said end of' the casing Ill. The outer end of said stem is screw-threaded and adjustably secured to an eye 20 which is locked in its adjusted position on the stem by a nut 2 I. One end of the cable-section a has fixedly secured thereto a fitting cr coupling 22 which is connected by a pin or bolt 23 to the eye 20 on the piston-stem I1. A cylir/fder 24 is formed in casingv I and extends from a shoulder 25 at the inner end of cylinder I I, which limits the movement of the piston I6 in one direction, to the end of the casing I0 which carries the packing I9. A sleeve 26'extends around the piston-stem I1 and has a flange 26 on its inner 'end which abuts against the inner face of piston I6. A coilspring 21 engages the end wall at the outer end of cylinder 24 and presses the sleeve into abutting engagement with one face of piston I6. 'I'he inner end of spring 21 is supported by the flange 26 of sleeve 26 to prevent it from sagging. Spring 21 has a predetermined force which exertsV pressure against sleeve 26 and through` said sleeve against one face of piston I6. Cylinders 24 and I I are filled With suitable hydraulic uid c. A filling-plug 29 is provided for loading said cylinders with said liquid. A small orifice 28 extends longitudinally through the piston I6 and permits the liquid to flow through the piston between cylinders I I and 24. Orifice 28 terminates at a channel in the inner end of sleeve 26. and the latter is sufficiently loose or has enough clearance around stem I1 to permit the liquid to pass back 'and forth between orifice 28 and cylinder 24. A iiexible diaphragm 3I closes the outer end of cylinder II and has its margin clamped between a shoulder 32 in head I2 and the end of casing Ill at the outer end of cylinder II. Head I2 is provided at the outer side of diaphragm 3| with a domed cavity 33. Said diaphragm and cavity form a closed air chamber. The diaphragm 3| and air chamber 33 provide a space to compensate for the reduced space for the liquid in cylinders 24 and II which-is caused by the inward movement of the stem I1 when the piston l' is shifted to take up slack in the cable and also serve to compensate for the volumetric changes of the fluid due to changes in its temperature.

In the use of the device shown in Fig. l the entire space in the cylinders 24 and II around stern I1 and piston I6 is filled with a suitable hydraulic fluid, usually a, non-freezing liquid. The piston-stem I 1 is coupled to the cable-section a by means of eye and pin 23 and the casing I0 is coupled to the cable-section a1 by means of head I2 and pin I5. The cable between the control and controlled elements to which the ends of the cable-sections are connected will then be adjusted in suitable manner, which may include,

the adjustment of the screw-connection between eye 20 and stem I1, to keep the cable-sections taut and under predetermined tension. The resistance value of the spring 21 selected is such that when the cable is under the desired tension for operation it will be under predetermined compression when piston I6 is seated on the shoulder in casing I0. This adjustment must be made when the airplane is at ground level where high temperatures usually prevail. When the airplane travels to higher altitudes where substantially lower temperatures' exist, the aircraft body will contract and shorten the distance between 4the elements to which the outer ends of the cable are connected. Unless compensated for, this contraction will slacken or undesirably reduce the tension on the cable. This contraction occurs at a slow rate. As it occurs, spring 21 will force the piston I6 to move outwardly in cylinder II. The orifice 28 will slowly permit the liquid in cylinder the connection is again under the desired tension for its desired operation. As the piston I6 is thus shifted, the stem I1 will reduce the Aliquid-space in the casing I0. To compensate for this reduction in area and any volumetric variation of the liquid caused by changes in its temperature, the diaphragm 3| will flex into the cavity 33 and increase the area of the space in cylinder Il. This operation will automatically maintain the desired predetermined tension on thecable. When the airplane again travels to lower regions of higher atmospheric temperature, the aircraft body will expand and increase the distance between the elements on the airplane which are connected-'by the cable. 'I'his increase produces a pull upon the cable-sections which will force I the piston toward shoulder 25 so that liquid will be slowly forced from the left hand side of piston I6 against the load of spring 21 to theright hand side of the piston, to automatically compensate for said expansion. As a result, the desired predetermined tension on the cable-connection will be automatically regulated or maintained to compensate for the expansion and contraction of the aircraft body. As the piston-stem I1 is moved out of the casing, the diaphragm. will flex to its normal position. The automatic device may be located at any desired point in the connection.

The connections in practice are usually subjected to sudden pull for operating the control element during the maneuvering of the airplane. This pull will be solidly resisted after the piston with the orifice therein has been shifted away from its normal position by the entrapped fluid between one side of the piston and one end of the casing, because the orifice is so small that the leakage of fluid therethrough will be negligible during the pull on the cable. The invention contemplates a slow cr restricted flow of hydraulic fiuid through the piston. If desired, a very slight clearance between the piston and the cylinder wall may be provided in lieu of an orifice extending through the piston.

Fig. 2 illustrates a modification in which provision is made for varying the rate of flow of hydraulic fluid through the orifice in the piston. The orifice is provided with a screw-thread. 31 for a screw 38 which has a slight clearance in said screw-thread. The inner end of the screw is provided with resilient fingers 39 for'v holding the screw in its set position inthe piston. By turning the screw into orcut ofthe screw-thread in the piston the rate of' flow through the orifice may be varied to permit trans- `fer of the fluid through the'piston at the opti- 1 mum or desired rate.`

The invention exemplifies a cable-connection.

adapted particularly for use in connection with aircraft whereby the desired tension on the cable for the control devices will be automatically maintained or regulated and forpreventing any slack in the cable which impairs or renders un- -piston extending through one end of the casing and connected to the other of the elements, UNITED STATES PATENTS the casing being provided with a chamber of less- 15 Number Name Date er diameter than the cylinder into which the 2,173,066 Clark oet. 31, 1939 v stern extends, and with a shoulder between the 564,351 Vaughan July 21. 1896 chamber and the cylinder, the chamber and cyl- 1,928,816 Grayson May 15, 1934 inder being lled with a fixed and predetermined 1,325,323 Ryder Oct. 6, 1931 volume of hydraulic fluid and disposed on both 20 1,761,747 Rosin et ai. June 3, 1930 sides of the piston, a spring in the casing for 682,536 Duncanson Sept. 10, 1901 shifting the-piston to hold the element under 381,731 Walker Apr. 24, 1888 predetermined iersion, means for restrictively 2,323,352 Pitts July 6, 1943 conducting the u d from one side of the piston to the other for controlling the movement of the 25 FOREIGN PATENTS piston by the spring and automatically compen- Number Country Date sating for the contraction of the structure to 1667/31 Australia May 1'?. 1932 i claim without departing vfrom the spirit and responsive to volumetric changes in the xed volscope ofthe invention.A ume of the iluid resulting from thermal expan- Having thus described the invention, what I sion and contraction of the uid for varying the claim as new and desire to secure by Letters Patl lcubical area of the chamber to compensate for ent is: 5 said expansion and contraction and maintaining An automatic tensioning device in a controlthe elements under said tension.

ling or shifting connection between elements supi ported by a structure which is responsive to con- JOHN L. ALDRED, Jn.

traction and expansion from temperature variations, comprising a. casing provided with a cyl- 10 REFERENCES CITED inder and connected to one of the elements, a The following references are af record in um piston movable in said cylinder, a stem for the me of this patent:

maintain the elementunder tension and means 700,009 France ----1 Dec. 17, 1930 

